Reddit is also the 6th most popular website in the world, and likely gets thousands of potential new users daily that are turned off by the design and don't become Reddit addicts.
This puts them just below Google, Youtube, Facebook, Baidu and Wikipedia[1]. That's absolutely huge. If the interface was so bad surely they wouldn't have been able to get there now, would they?
[1] https://en.wikipedia.org/wiki/List_of_most_popular_websites